Whenever a hole is drilled into an article, it is intended for the bit of the drill to enter the article at some predetermined angle of orientation with respect to the surface of the article. The precision with which the actual angle of orientation of the bit must be relative to the predetermined angle of orientation depends upon each application, and can vary from high accuracy to just approximate accuracy.
In the majority of cases, the drilling of a hole at a precisely accurate orientation angle is accomplished using a drilling fixture, as for example a drill press, which exactly provides the predetermined orientation of the of the drill bit with respect to the surface of the article being drilled. The task of providing an accurate drill hole, however, becomes difficult if the drill is hand-held and the drilling is to be performed without the assistance of a drilling fixture. Hand-held drills are extremely ubiquitous, and are used for a plethora of small jobs around the shop or house. Most frequently, the need is to drill holes which are exactly perpendicular to the surface of an article to be drilled by a hand-held drill. And, what further complicates the precision of such perpendicular drilling is that the surface involved may not be flat, as for example a corner, or a curved surface.
The need for an auxiliary fixture enabling the drilling of holes at a specified angle to the work surface using a hand-held electric drill has been long recognized. One common approach is to attach a hand held electric drill to a fixture having a base that can be position on the work surface. The top of the fixture holding the drill can be tilted with respect to its base to set the desired angle, thus tilting the drill to the same angle. In addition, the fixture allows the affixed drill to freely slide along the length of the fixture. The drill is pushed toward the work surface and drills a hole at the preset angle. Examples of this general concept are disclosed in U.S. Pat. Nos. 2,831,376; 3,534,639; 3,890,058; 4,199,283; 4,391,558; and 4,842;453; wherein U.S. Pat. Nos. 4,199,283 and 4,391,558 provide examples of setting compound angles. Fixtures based on this concept are large, complex, cumbersome and not applicable to small surfaces. Also, they can be more expensive than the hand-held drill itself.
Another common basic concept represented in the prior art is a fixture clamped to the article to be drilled. The hand-held drill has a drill bit guided through a properly sized and tilted hole in the fixture. These fixtures are usually designed for specialized applications and are usable only with work pieces of a specific geometry. Examples of these fixtures are disclosed in e.g. U.S. Pat. Nos. 3,626,513; 4,257,166; 5,322,396 and 6,116,826.
Therefore, what remains needed in the art is a simple and inexpensive hand-held drill bit guide that can be conveniently used with electrically powered hand-held drills to provide a precisely perpendicular orientation angle with respect to the surface of an article to be drilled, wherein the surface may be flat, cornered or otherwise generally non-planar, e.g. convex, concave, cylindrical, etc.